<?php
namespace EasyTask\Cron;

/**
 * Abstract CRON expression field.
 */
abstract class AbstractField implements FieldInterface
{
    /**
     * Full range of values that are allowed for this field type.
     *
     * @var array
     */
    protected $fullRange = [];

    /**
     * Literal values we need to convert to integers.
     *
     * @var array
     */
    protected $literals = [];

    /**
     * Start value of the full range.
     *
     * @var int
     */
    protected $rangeStart;

    /**
     * End value of the full range.
     *
     * @var int
     */
    protected $rangeEnd;

    /**
     * Constructor
     */
    public function __construct()
    {
        $this->fullRange = range($this->rangeStart, $this->rangeEnd);
    }

    /**
     * Check to see if a field is satisfied by a value.
     *
     * @param string $dateValue Date value to check
     * @param string $value Value to test
     *
     * @return bool
     */
    public function isSatisfied($dateValue, $value)
    {
        $dateValue = (int)$dateValue;
        if ($this->isIncrementsOfRanges($value))
        {
            return $this->isInIncrementsOfRanges($dateValue, $value);
        }

        if ($this->isRange($value))
        {
            return $this->isInRange($dateValue, $value);
        }

        return '*' === $value || $dateValue === (int)$value;
    }

    /**
     * Check if a value is a range.
     *
     * @param string $value Value to test
     *
     * @return bool
     */
    public function isRange($value)
    {
        return false !== strpos($value, '-');
    }

    /**
     * Check if a value is an increments of ranges.
     *
     * @param string $value Value to test
     *
     * @return bool
     */
    public function isIncrementsOfRanges($value)
    {
        return false !== strpos($value, '/');
    }

    /**
     * Test if a value is within a range.
     *
     * @param int $dateValue Set date value
     * @param string $value Value to test
     *
     * @return bool
     */
    public function isInRange($dateValue, $value)
    {
        $parts = array_map(function ($value) {
            $value = trim($value);

            return $this->convertLiterals($value);
        },
            explode('-', $value, 2)
        );

        return $dateValue >= $parts[0] && $dateValue <= $parts[1];
    }

    /**
     * Test if a value is within an increments of ranges (offset[-to]/step size).
     *
     * @param string $dateValue Set date value
     * @param string $value Value to test
     *
     * @return bool
     */
    public function isInIncrementsOfRanges($dateValue, $value)
    {
        $dateValue = (int)$dateValue;
        $chunks = array_map('trim', explode('/', $value, 2));
        $range = $chunks[0];
        $step = empty($chunks[1]) ? 0 : $chunks[1];

        // No step or 0 steps aren't cool
        if (null === $step || '0' === $step || 0 === $step)
        {
            return false;
        }

        // Expand the * to a full range
        if ('*' === $range)
        {
            $range = $this->rangeStart . '-' . $this->rangeEnd;
        }

        // Generate the requested small range
        $rangeChunks = explode('-', $range, 2);
        $rangeStart = $rangeChunks[0];
        $rangeEnd = empty($rangeChunks[1]) ? $rangeStart : $rangeChunks[1];

        if ($rangeStart < $this->rangeStart || $rangeStart > $this->rangeEnd || $rangeStart > $rangeEnd)
        {
            throw new \OutOfRangeException('Invalid range start requested');
        }

        if ($rangeEnd < $this->rangeStart || $rangeEnd > $this->rangeEnd || $rangeEnd < $rangeStart)
        {
            throw new \OutOfRangeException('Invalid range end requested');
        }

        // Steps larger than the range need to wrap around and be handled slightly differently than smaller steps
        if ($step >= $this->rangeEnd)
        {
            $thisRange = [$this->fullRange[$step % \count($this->fullRange)]];
        }
        else
        {
            $thisRange = range($rangeStart, $rangeEnd, $step);
        }

        return \in_array($dateValue, $thisRange, true);
    }

    /**
     * Returns a range of values for the given cron expression.
     *
     * @param string $expression The expression to evaluate
     * @param int $max Maximum offset for range
     *
     * @return array
     */
    public function getRangeForExpression($expression, $max)
    {
        $values = [];
        $expression = $this->convertLiterals($expression);

        if (false !== strpos($expression, ','))
        {
            $ranges = explode(',', $expression);
            $values = [];
            foreach ($ranges as $range)
            {
                $expanded = $this->getRangeForExpression($range, $this->rangeEnd);
                $values = array_merge($values, $expanded);
            }

            return $values;
        }

        if ($this->isRange($expression) || $this->isIncrementsOfRanges($expression))
        {
            if (!$this->isIncrementsOfRanges($expression))
            {
                $exResult = explode('-', $expression);
                $offset = $exResult['0'];
                $to = $exResult['1'];
                $offset = $this->convertLiterals($offset);
                $to = $this->convertLiterals($to);
                $stepSize = 1;
            }
            else
            {
                $range = array_map('trim', explode('/', $expression, 2));
                $stepSize = empty($range[1]) ? 0 : $range[1];
                $range = $range[0];
                $range = explode('-', $range, 2);
                $offset = $range[0];
                $to = empty($range[1]) ? $max : $range[1];
            }
            $offset = '*' === $offset ? $this->rangeStart : $offset;
            if ($stepSize >= $this->rangeEnd)
            {
                $values = [$this->fullRange[$stepSize % \count($this->fullRange)]];
            }
            else
            {
                for ($i = $offset; $i <= $to; $i += $stepSize)
                {
                    $values[] = (int)$i;
                }
            }
            sort($values);
        }
        else
        {
            $values = [$expression];
        }

        return $values;
    }

    /**
     * Convert literal.
     *
     * @param string $value
     *
     * @return string
     */
    protected function convertLiterals($value)
    {
        if (\count($this->literals))
        {
            $key = array_search(strtoupper($value), $this->literals, true);
            if (false !== $key)
            {
                return (string)$key;
            }
        }

        return $value;
    }

    /**
     * Checks to see if a value is valid for the field.
     *
     * @param string $value
     *
     * @return bool
     */
    public function validate($value)
    {
        $value = $this->convertLiterals($value);

        // All fields allow * as a valid value
        if ('*' === $value)
        {
            return true;
        }

        if (false !== strpos($value, '/'))
        {
            $exResult = explode('/', $value);
            $range = $exResult['0'];
            $step = $exResult['1'];
            // Don't allow numeric ranges
            if (is_numeric($range))
            {
                return false;
            }

            return $this->validate($range) && filter_var($step, FILTER_VALIDATE_INT);
        }

        // Validate each chunk of a list individually
        if (false !== strpos($value, ','))
        {
            foreach (explode(',', $value) as $listItem)
            {
                if (!$this->validate($listItem))
                {
                    return false;
                }
            }

            return true;
        }

        if (false !== strpos($value, '-'))
        {
            if (substr_count($value, '-') > 1)
            {
                return false;
            }

            $chunks = explode('-', $value);
            $chunks[0] = $this->convertLiterals($chunks[0]);
            $chunks[1] = $this->convertLiterals($chunks[1]);

            if ('*' === $chunks[0] || '*' === $chunks[1])
            {
                return false;
            }

            return $this->validate($chunks[0]) && $this->validate($chunks[1]);
        }

        if (!is_numeric($value))
        {
            return false;
        }

        if (\is_float($value) || false !== strpos($value, '.'))
        {
            return false;
        }

        // We should have a numeric by now, so coerce this into an integer
        $value = (int)$value;

        return \in_array($value, $this->fullRange, true);
    }
}
